Wood cutting router bit



June 1934. H. P. BRUMELL El AL 1,963,611

- TER BIT Filed March 5. 1932 Wvfiol Harry P52" all I Leroy Emma/ U Patented June 19, 1934 I WOOD CUTTING ROUTER BIT Harry P. Brumell, New Britain, and Le Roy- E- Linsley, Plainville, Gonn., assignors to The Stanley Works, New Britain, Conn., a corporation of Connecticut Application March 5, 1932, SerialNo. 596,928

2 Claims. (c1. 144-219) This invention relates to'router bits and, parburned by friction with resultant danger to the ticularly, to side cutting bits for forming grooves, tool, but, with our improved spiral bits, this effect slots, or the like in wood and similar materials. is eliminated. Y

It has been the universal practice to provide Other objects will be in part obvious and in 1 5; router bits for cutting grooves, slots, etc., in wood part pointed out more in detail hereinafter. v and the like with substantially straight cutting The invention accordingly consists in the feaedges, but such bits have numerous disadvantages tures' of construction, combination of elements and objections due to the character of the cuts and arrangement of parts which will be exempli v taken and the failure of the bits to clear the chips fied in the construction hereinafter set forth and =-from the cut and, therefore, such bits have limithe scope of the application of which will be 65 "tations in their uses. With standard straight indicated in the appended claims. fluted bits, each cutting edge, through a length ,In the accompanying drawing, wherein is shown equal to the depth of the cut, comes, at once, into one embodiment which the present invention engagement with the work resulting in a gouging may take:

5 -action, so to speak, and setting up shocks and Figure l is an enlarged side elevational View 7 "strains in the bit and the work; also, the chips of the bit;

generated accumulate in the cut in a more or less Fig. 2 is a transverse section through the bit packed condition since, they. occupy a greater taken on a, plane normal to the axis and inchspace than the original material from which they cated by the line 2-2 of Fig. l;

are formed. Swing to these deficiencies, the Fig; 3 is a fragmentary cross sectional view 75 depth to which a straight fluted router bit can cut taken on a plane which is at right angles to the is limited; the speed of cutting is limited due length of the cutting edge and which plane'is tow the danger or" breaking the bit and damaging designated by the line 33 of Fig. 1; v the wood; considerable power is required; the Fig. 4 isa forward end view of the router bit;

cut taken is relatively rough and burred, and in and r v 0 A trioate shapes'cannot be out where the material Fig.5 isa fragmentaryviewshowingthe forward left at the side of the cut is thin in cross section. portion of the bit in side elevation,'this view being The aimof the present invention is to provide taken on aplane substantially at right an les to a side cutting router tool which is far superior that on which Fig. 1 is taken.

in its action than a standard straight fluted Referring to the drawing in detail, the router router bit, and which is not open to the above is shown as having a shank A and an aligned and other disadvantages and objections. cutter portion, the latter being provided with a More particularly, the aim of the invention is plurality of spiral threads 10 each provided with to provide a router bit with spiral side cutting a cutting edge 11, there being two such threads 35 edges so arranged and proportioned that the shown in the present instance. It is to be unedges, when the tool is fed laterally, will take derstood, however, that the tool may have more smooth slicing cuts in the work and rapidly clear than two threads. The helix angle of each cutthe chips from the out being taken. With this ting edge is such that these edges will have a improved arrangem nt, the speed of cutting may slicing or shearing action of the most efiicient 40 be materially increased, and the depth of cut may character and will effectively remove the chips be greater than has heretofore been possible, instantly so that no trouble will be experienced A very smooth finish is obtained and very intriwith the chips clogging the cutter. We have cate designs may be made having thin strips, finfound the helix angle of the cutting edges should gers or ribs between successive cuts across the be at least 30, and, preferably, between 30 and grain of the wood. Our improved bits require 40, the best results probably being obtained less power, and bit breakage is reduced to a minwhen the angle of helix is between 33 and 3'7.

imuin. A spiral bit constructed in accordance In the drawing, the angle of helix is illustrated with the present invention will maintain a keen as being approximately 33. The spiral cutting sharp cutting edge longer than the standard edges are given a very substantial angle of rake,

straight fluted bits, and they are less hazardous the angle of rake preferably being about 30 to operate as they will not tend to dig and tear taken normal to the cutting edge, as shown most the piece being worked on from the operators clearly in Fig. 3. The lands or threads may have hand. Furthermore, with a standard straight a suitable clearance which is preferably between fluted bit, if the operator stops feeding the work 8 and 10 to the tangent, as shown most clearly 55 for only an instant, the work will be discolored or in Fig. 3. The cutting threads or lands may, of no course, be either right or left handed, as desired. The length of the cutting portion of the bit, as compared to its diameter, may be considerably longer than bits as heretofore made in order to take a relatively deeper cut, in the present instance, the length of the cutting portion of the bit being substantially flve or six times its diameter. The bit, in use, is adapted to be driven at a relatively high speed, it being found it can be efficiently employed at 9,000 to 20,000 R. P. and it can be driven at a lip speed of substantially 600 feet per minute. In the drawing, the bit is shown on an enlarged scale.

In using our improved bit, suitable templates may be employed for guiding the same; cuts may be taken either in one surface of the work or entirely through the work; and the cutting action may be started at the edge of the work or within the edge of the work. Where the cutting operation starts at the edge of the work, the cutter may be fed laterally up to and into the work whereas, when starting a out within the edge of the work, the tool may be first fed down to the desired depth and then moved laterally. When a design is to be cut by following a facsimile thereof laid upon the material, left hand bits may be employed which will leave not burr on the top surface of, the work. During the cutting operation, the cutting edges take shearing or slicing "cuts and, in ordinary routing operations where the depth of the cut equals or exceeds the pitch of the cutting edges, one blade or cutting edge is constantly engaged with the work, thus eliminating shock caused by the cutting edges of the standard straight fluted bit when such edges come into contact with the work. This minimizes bit breakage due to flexing of the bit or crystallization, and is one of the features which permits of cutting thin deep cross sections. At recommended speeds at which the spiral bits should be used, the spiral lands act as screw conveyors for clearing the chips from the cuts so that clogging of the cutter and resultant re-' sistance thereto is, to a large extent, eliminated. With our arrangement, the chips are carried away so rapidly that the spiral cutter acts, to some, extent, like a fan causing a circulation of airwhich keeps both the bit and the wood cool.

Thus, if the operator should stop feeding the work and tool, one relative to the other, discoloration or burning of the wood by friction would not result, and thus one objection to straight fluted tools is eliminated.

It is thus clear that our improved tool has various features of novelty and advantage which permit of increased efficiency and the production of better, smoother and more accurate and intricate work, and that cuts of greater depth at greater speeds and with less danger of breakage of the bit or damage to the work may be taken with the use of less power than has heretofore been possible. The bits are able to cut in depth up to six times their diameters in hard wood. Due to the slicing action of the cutting edges and the elimination of chip accumulation in the cuts, very intricate designs may be made, leaving a strip or rib of cross-grained wood between the "cuts as thin as one-fourth to one-half the diameter of the bit and as deep as the cutting capacity of the bit.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

We claim as our invention:

1. A side cutting router bit for cutting wood and the like and having a plurality of spiral cutting edges provided with an angle of helix of at least thirty degrees and an angle of rake of substantially thirty degrees.

2. A side cutting router bit for cutting wood and the like and having a plurality of spiral relieved cutting edges each having an angle of spirality of substantially thirty-three degrees and an angle of rake of approximately thirty degrees.

HARRY P. BRUMELL. LE ROY E. LINSLEY. 

